In the finishing of the bodies of vehicles it generally is required to sand the putty or filler used prior to painting. Dry sanding often leaves scratches and other aberrations which are not always completely hidden by the coats of paint. In addition, considerable dust is discharged into the atmosphere of the repair shop, creating health hazards for the workmen. Accordingly, it has been proposed (see, for example, U.S. Pat. No. 3,395,495) to resort to wet sanding in order to finish the surfaces of the vehicle body in preparation for painting. In some systems a spray bar directs the stream of liquid across the top of the abrasive wheel, thereby resulting in the loss of liquid prior to the time it reaches the surface being sanded and also introducing a quantity of liquid into the machine itself, thus requiring a special water-tight construction for certain of the machine elements which might otherwise be damaged through exposure to the liquid. Further, since there is a substantial distance between the spray bar and the surface to be sprayed, excess quantities of liquid may be required in order to insure the provision of the desired amount of liquid on the work surface of the vehicle.